Briefly stated, this invention relates to electrooptic displays of the electrochromic type, and more particularly to an improved construction for a thin electrochromic display.
Electrochromic displays are known which employ electrochromic material on spaced parallel substrates with porous separating material between the substrates carrying the electrolyte and pigment material providing contrast for the segments. Such a display is shown in U.S. Pat. No. 3,944,333 issued Mar. 16, 1976 in the name of Marshall Liebowitz and assigned to the present assignee, which is incorporated herein by reference. Such displays having two substrates or supporting plates prove to be thick and bulky. Other examples of electrochromic displays with two substrates and porous or fibrous separators are shown in U.S. Pat. No. 3,892,472 issued to Giglia on July 1, 1975 and U.S. Pat. No. 3,840,288 issued to Schnatterly on Oct. 8, 1974. Such constructions have generally employed some sort of external seal between substrates, such as epoxy resin or the like.
An alternate approach is to contain electrolytes of liquid or gel between the substrates. Since these materials are fluid and not self-supporting they require peripheral spacers between substrates to contain the electrolyte and seal the display as well as providing spacing between the substrates. Such constructions are shown for example in U.S. Pat. No. 3,879,108 issued Apr. 22, 1975 to Baritz, or U.S. Pat. No. 3,704,057 issued Nov. 28, 1972 to Beegle, these being merely exemplary of many.
Electrochromic displays have been described utilizing only one transparent substrate, with the active elements applied as layers to the substrate. Examples of these are U.S. Pat. No. 3,971,624, issued July 27, 1976 to Bruesch et al, and U.S. Pat. No. 3,995,943 issued Dec. 7, 1976 to Jasinski, these patents showing metal layers applied over solid electrolyte layers. The electrolyte layers perform the spacing function. The foregoing patents require special means for sealing the back electrode metal layers and making electrical contact thereto.
It would be desirable to have a thin electrochromic display construction, utilizing only a single substrate, with a simple means for applying and sealing the back electrode to contain the electrolyte, maintaining suitable spacing, providing proper contact of the electrolyte with the electrochromic material on the segments, carrying the contrasting pigment, and facilitating cationic transport to and from the electrochromic material.
Accordingly, one object of the present invention is to provide an improved construction for a thin electrochromic display.
Another object of the invention is to provide an improved construction for sealing an electrochromic display and containing the electrolyte.